1. Field of the Invention
This invention relates to a sealing structure, a method of soldering and a process for preparing a sealing structure. More particularly, the present invention is concerned with a soldering technique which can simplify surface treatmentn of ceramic and is suitable for use in the field of electronic components, semiconductor components, etc. where soldering of ceramic and metal is desired.
2. Description of the Prior Art
Known methods of soldering metal and ceramic include (1) a method typified by the polybdenum-manganese (mo-Mn) process or copper sulfide process, which comprises coating the surface of ceramic with metallic powder through baking (metallization) and plating the metallized portion with nickel (Ni) followed by gold (Au), or chromium (Cr) followed by nickel and then gold to thereby facilitate soldering and (2) a method which comprises soldering metal and glass or oxide ceramic using a solder comprising lead-tin (Pb-Sn) as the main component and zinc (Zn), antimony (Sb), silicon (Si), titanium (Ti), beryllium (Be) and rare earth elements added thereto.
Also, a sealing structure for sealing electronic components, for example, which is formed by soldering a square casing composed of a ceramic member with one side thereof opened, and a board, is known.
The above-mentioned soldering methods have the following drawbacks. Since the former method requires metallizing treatment of the ceramic, strict control of the atmosphere for metallization and plating treatment after the metallization are indispensable. Further, this method has limitations due to the complexity of procedures and also tends to cause defects such as pore formation on the metallized surface. In the latter method, the ceramic which can be used is limited to glass and oxide ceramic, and no satisfactory result can be attained with respect to the soldering of non-oxide ceramic, e.g., silicon carbide (SiC) or silicon nitride (Si.sub.3 N.sub.4), and metal.
Meanwhile, in the above-mentioned sealing technique, a square casing with one side thereof opened is formed of a single ceramic member. Therefore, when the provision of projections within the casing is intended in order to release heat generated from electronic components, great difficulties are encountered in fabricating projections within the casing. Even if the projections are successfully provided within the casing, their shapes are limited to simple ones. In this sealing technique, the edge portion of the casing is plated with nickel (Ni) or gold (An) and soldered to the ceramic board, thereby forming a sealing structure.